Manufacture of an improved tall oil



Patented 18,1941

This invention rent to a processor resume crude tall oil. lit is wellknown in the wood pulpin: that when the black liquor obtainedi'rom thepulping of coniferous woodby v the sulphate procws is evaporated, ascum. com-' mcnly mown as tall oilsoep, separates and floats upon the oftheblack liquor; scum is not present on the liquors o-s t y obtainedbefore the evaporation step, but]: pro; du' probably by'a salting outerect, the liquor becomes concentrated. In present puoctice the scum oftall ,oil soap is skimmed oil of the;

evaporated black liquor sndeither used as to produce crude sodium saltsof tell oil or more frequently the scum is treeted'totformfcrude(chemical constituents of the exudation are comtall oil. The crude telloil soepis usually treeted withdilutesolutions of sulphuric acid orsodium acid sulphate to liberatethis crude tall oil;

In orderto facilitate the sepamtlon'ofthe mixq ture into two layers,,the,use of with the aoidto increase" thedens'ityof the I water leyeriscommon practice; Aiter the acid.

f hasreaeted the crude tall oil is theupper layer and canbeseparated-from the lower aqueouszs sodimn sulphate layerbyodeoantstion or any other suitable means commonly used in the'chem-'icaiindustries. i

Crude tall oil, prepared in the above manner,

, is of limited usefulness in industrial imitation.

an It posseses the "foul odor typicalof suljphwte black liquors; "it, ofdarkcolor;

and. an even greater; objection is its tendency to vpartially, Poducing-is thick couspastedifilcult to pump anddiulcultfto re- I move tomshlpping' 'contalners. Mllstendency to crystallize varies dependingupon the" history of the wood from which it originates Conse quently,crude tall oil lacks uniformity in chemical composition'and physicalcharacteristics.

It is the purpose {of ithisinvention to provide 9, simple economicalprocess by which taliofl can a e mn e m w mi e hy ical appearance withan improved odorsnd colori'as compared to the crude oilnow found incommerce. The improvedtall oil producedin accordence with'in P c to bedeswlbedhemmatter has been found to be free of those cryfs talline whichoccurin the crude prod- H v q q q crude tall onshowsmoreorystalformaltion than does the untreated product. r 0

not and consequently is a smooth uniform oily Pro uct. 'It*'is" capableof standing in storage I indefinitely without crystallization."

'To understand the advantages offered by this 7 invention it isessential to appreciate the lack of uniformity found in tall ollresultinz from the 5 variations inthe kind or woodused in the Q88, andmore panticularlyfrom mum in the history of this, wood. when southernpine is 1 pulped by the'sulphate process promptly after it is cut green,yields a tall oildifterent from' that produced the, loss are puipedafter I they have been out and exposed to air for months. When apinetree is out it exudes resmous matter in an attemptto seal the wound.This necessarily places "a. large portion of the resinouscontentlof'tl'lewood in withthelo' air. and utter longexposure the airpenetrates the ,wood and oxidizes some of the constituents plex and ofmany types, the'che'mical changes by oxidation srenot entirelyunderstood.

Experience has 'proyed'also that in the of fattyacids to the resin acidsis considerably b1813 thanin the tall oilobtained by pulping woodwhichhas been cut inthe winter when' the sap is out of the tree. Becauseof these variations me the wood used, crude m1 oil so: u

' wood; These variations have retarded the ingo dustrial application of.crude tall oil.

Experimentation has shown that sbietlcacid toh'ydrOXyabieticacid undermild 0x1- dlzinmconditions. This can occur to a certain extent'when theconiferous woods'tends exposed u to air utter being, cut. Hydroxyebieticacid is less soluble .in fatty acid than is abietic and consequently. ittends to crystallize out of crude tall oil. crystals probably act as a.nuclei for the crystal growth of other resinous P oducts 0 present inthe nude telloil. In' any event hydmxyebietic acid is believed'toaccountfonthe partial solidiflwtlon of crude tall oijldue to'crys- It isone of the objects of this invention to eliminate the presence '-ofhydroxyabietic acid and other oxidized analogous orilrelated' com poundsand derivatives bychemlcally processing the crude tall oil; 11 heat thecrude telloil, -'at u r wood cutln the spring of the year the ratio afirst rather slowly, to drive oil water which is not chemically boundand some low-boiling odorous I then continue the heating progressivelyuntil a maximum temperature of 250450" 0. has been attained. I usuallypre fer to maintain a temperature of at least about 300 for atleast anhour inor'der that the chemical reactionswhich occur during may besubstantially completed. Care is taken that the tall oil does notcome incontact with air during the heating operation and. that the vaporizedproducts are removed. After the mei chanicaily held water has beendriven away the volatile products coming from the heated tall oil showan increasing volume of vapor as the temperature rises. This vapor issubstantially all water, formed by pyrolysis, and also contains sulphurbodies coming from the ligninand other sulphur compounds always presentin crude tall. oil as impurities. I

A variety of procedures may be employed in the heating operation as'willbe apparent to one 7 skilled in the art. I have found it advantageoustoheatthetalloilintwosi:ages,firsttoaternperature in the neighborhood of100 C. to remove free water and readily vaporizable con- "stituents andthen to about 325' C. to effect the chemical changes described. Eachheating stage advantageously is accompanied by a flow! U ing of theheated material. in a thin layer over a splash plate or the like tofacilitate the re-' moval of volatile constituents. In some in.- stancesI have found it desirable to maintain a temperature of 325 C. foraboutil hours.

Ifthetalloilisdryatthestartthelossof' tall oil as a result of theheattreatment gener found to be changed from a yellowish-,brownto aniridescent green, 9. color similar to that ob-' served in petroleumlubricating oils. Also the odor is decidedly improved'because of thesubally does notexceed 5%.

The heating of the crude tall'dl-rmlts in a product which will be foundto havaehanged chemically and physically in characteristics. In thefirst place, its color after cooling will be stantial loss ofsulphurcompounds found in crude tall oil. a burnt or charred organic substance.This odor, I believe,.is due to the charring of small traces of ligninusually present in tall 011. Although it is not necessary in carryingout my process, I may remove this burnt fodor by, treatment withhydrogen in the presence of a catalyst in the usual manner common inhydrogenation of oils. While one may continue the treatment withsufficient hydrogen to hydrogenate the fat-.

ty and resin acids, as well as the odorous materials, this is notessential as, the odorous materials appear to be converted tonon-odorous products rapidly by hydrogen treatment. I also appreciatethe possibility of removing these odorous materials by many of the knownmethods used in the art,- such as superheated steam, activated carbon,etc. Filtration for the removal of solid matter is not necessary. .Theconstituents which normally result in the deposition of solids j fromcrude tall oil apparently are destroyed or rendered more soluble orremoved by. distillation during the heating andvaporizing treatmentdescribed.

Probably the major change which occurs in crude tall oil whenprocessedas described is the lowering of the resin acid contentof theoil and the simultaneous substantial increase in the unsaponifiablecontent in the oil. Merely, as a mat- The derived odor is suggestive ofV asssaes ter of possible explanation I ofler the following theory toaccount for this chemical change during the process. Hydrozvabietic acidhas been found to be unstable at temperatures of 200' C. and higher. It'is believed that the oxidized products in crude tall oil, among'whichis probably hydroxyabietic acid, become dehydrated during the heatingprocess. This produces anhydrohydronabietic acids and possibly poymerized or isomerized colophonic acids. Evidence indicates that some ofthe carbonyl groups of'these resin type acids are destroyed in theheating process. Any one ofthe above conditions would account for thelower acid number found on theheated product, as well as the increasedunsaponiflable value. It appears also that abietic acid if presentprobably is converted to the more stable pyroabietic acid.

The following table shows the changes produced by the above describedheating and va- Theimproved'odor, together with the relativelyincreasedpel' cntage of fatty acids, has rendered the, product suitablefor use in the manufacture of such commercialarticles as soaps,printinginks,

greases, rubber compounds, etc, where the crude tall oil hasnever beenfound adaptable. I

After deodorizlng with hydrogen as described above theproduct' hasadefinitely sweet fatty odor fax-more desirable than the foul odor of thecrudetalloil.

The product is characterized physically, by its improved odor comparedto tail oil and by its freedom from any tendency to crystallize'o'nstanding. Chemically it appears to be, most distinctly characterized byits freedom from hydroxy abietic acid.

I claim:

1. Process'for the production of refined tall oil which is a smooth.uniform, oily liquid capable of prolonge'dstanding withoutcrystallization which consists in raising the temperature'of, crude talloil from coniferous wood to a maximum between about 250 C.'and about 350C., said heating operation'serving to vaporize and expel mechanicallyassociated water, water produced by Pyrolysis, low boiling odorousmaterials and sulfur'compounds,

. the loss by vaporization from tall oil which is dry at the beginningofthe heating operation generally not exceeding 5 and separating theresidual liquid from the vaporized materials.v

2. Process as defined in claim 1 in which the crude tall 011' is firstheated slowly todrive of! mechanically associated water and some lowboiling odorous materials and then is heated progressively to a'maximumtemperature of 250-350 C. and the heating iscontinued at saidtemperature for a time suflicient to permit completion of chemicalreactions occurring at said temperature.

' 3. Processes defined in claim 1 in which the heating at said maximumtemperature is carried out at atleastabout 300 C. for at leastabout 1hour.. y

4. Process as defined in claim 1 inwhich the heating at said maximumtemperature is atabout 325 C. for about 3 hours.

l needed:

1 in whiclialr isaboutfos aby weight or the weight of the dry "crudetail oil and containing the organic products oi p rroiysiaot the hydroxyabietic acid content of the crude tall oil. 1

8. Refined tall 011 as defined in claim '1 having,

as compared with crude tail oil lower acid number, saponificationnumber, resin acid content and iodine number and higher fatty' acidcontent and unsaponifiabie content. 9. Refined tall oil as substantiallyfree of hydroxy abietic acid. HAROLD R. 'MURDOCK'.

defined in claim v being 10

